Reaper of the Drifting Moon - Chapter 267

A scientific genius named Thomas Harrier was transmigrated to an imperial prince body after a car accident that took his life. He found out that he is in a world similar to our own with a timeline akin to early twentieth century. The body that he is occupying was the imperial prince of a failing empire who suddenly rose to power after a successful assassination attempt of his father. Unaware that the attack is just the beginning of what is to come. He faces many challenges throughout. Will Thomas Harrier be able to live his second life in peace while running an empire and getting it back to its former glory? Or will he succumb into a conspiracy lurking within the country's borders?

Expect some:

Cold war era techs.

Super battleship with advanced electronics, propulsion, and fire control systems?
Helicopters?
Missiles?
Modern medicines and equipment?
AC-130?
A nuke?
Challenger or Abrams or Leopard?
F-4 Phantom or MIG-21?
Colored TV's.

Everything!!!

PS. Cover not mine, I just found it on google.

When a cold and crafty girl travels into the body of a foolish, man-crazy, young female aristocrat, what will happen?

“Hey, Yoshi-kun. I think you’re——”

Hearing that voice for the first time stopped me in my tracks. On my way home from school. On the playing field of our junior high, and at the bookshop in front of the station. And then in the empty lot where the white cat slept. Shiina Yuki, the strange girl who somehow knew all about me, always approached me like that.

We laughed, cried, got angry, held hands. Again and again, we repeated those disappearing memories and ephemeral promises. That’s why I never knew. I never knew the value of Yuki’s smiles or the meaning of her tears. Nor even the singular sentiment behind her many ‘Nice to meet you’s.

This is a captivating, heartrending tale of meetings and partings.

Originally born from a wealthy family, she ends up leading a vagrant life for fifteen years. However, when she is eventually found by her family, she falls into another devious plot and eventually dies tragically.

Fifteen years after her rebirth, ravenously raging for revenge, she tears down the hypocritical mask of the foster daughter who had taken her place, and reduces her greedy stepmother and stepsister back to their original sorry states.

To the jerk’s profession of his deep love for her, she only has one thing to say, “Get the hell out of my life. The love you speak of humiliates love!”

Regardless of the appearances of you monsters, I’ll take in it my stride with my capability, building a business dynasty of my own, sitting in the depths of my riches, bathing in the glistening limelight of the world.

A certain rich empire’s CEO: “Don’t mind me. I’m just leaving my mark here to declaring my possession rights; I’ll wait patiently for you to grow up!” The queen’s mighty return with commercial warfare fully within her grasp, she navigates the power struggles with skill and verve. When it comes to scheming conspiracies, all she has to say is, “Who are you again? Don’t even bother!”

- Description from Novelupdates